I don't know why the programmers chose to ignore the possibility of rotating the IBL light probe but they did. Mathematically its a relatively simple operation. However, rotating the light #1 WILL affect your preview - it will light the preview as if it were an infinite light. Because of this, I sometimes move it around a little to help me judge what I'm seeing in the preview and be better able to predict the influence of other lights. Test renders are key here, though. Don't trust the preview for much where lighting is concerned.

Sorry I can't give dial settings for angles - I'm away from my poser machine until Monday.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)